1. Technical Field
The present invention relates to a resonator element which excites thickness shear vibration, and a resonator, an electronic device, an electronic apparatus, and a moving object using the same.
2. Related Art
Since an AT cut quartz crystal resonator that excites thickness shear vibration which is main vibration is suitable for miniaturization and increasing a frequency and exhibits a cubic curve which has an excellent frequency-temperature characteristic, it has been used in various fields such as oscillators and electronic apparatuses. Particularly, in recent years, as the processing speed of transmission communication equipment or OA equipment is increased or the volume of communication data and the processing capacity are increased, there has been a strong request for increasing a frequency for the AT cut quartz crystal resonator which is a reference frequency signal source used therein. For increasing the frequency of the AT cut quartz crystal resonator that excites the thickness shear vibration, it is common to increase the frequency by reducing a thickness of the vibrating portion.
However, if the thickness of the vibrating portion is reduced along with increasing the frequency, the adjustment sensitivity of the frequency is increased, and thus there is a problem of a final frequency accuracy being poor and the production yield of a resonator being lowered. In contrast, JP-A-2002-111435 discloses a resonator element of a temperature compensated oscillator in which four corners of an excitation electrode having a rectangular shape are cut out to be substantially equal and the ratio of an area after cutting to an area before cutting is set to be 95% to 98%, which allows the capacitance ratio γ of the resonator (=C0/C1, here, C0 is an equivalent parallel capacitance, and C1 is an equivalent serial capacitance) to be reduced, and the frequency variable sensitivity is increased, which allows a margin for fitting the oscillation frequency to be increased.
However, since there is a high possibility of the main vibration being coupled with spurious vibration due to a variation in a plane parallelism degree of the thickness of the vibrating portion and a frequency jump phenomenon occurs, there is a problem of oscillation being unstable.